Initiation of incrustation by collision between crystals and a solid surface is investigated. The suspension flow towards the vessel wall in a crystallizer is simulated by laboratory experiments. A liquid jet of supersaturated suspension impinges on a plate at well defined hydrodynamics, supersaturation and parent crystal size. Experiments have been carried out with succinic acid/water. The results indicate that crusts may be initiated at supersaturation well below the metastable limit. Crusts are initiated on both Teflon(TM) and steel. More crust nuclei are formed by collision initiation on sanded stainless steel than on polished stainless steel or Teflon(TM). The results support the hypothesis that collision initiation of crusts is of industrial importance, and suggest that attention should be devoted to the hydrodynamics of crystallizers.